The notion of a picture being worth a thousand words can often be an understatement. Witness the newest, just-released photo of Saturn captured by the Hubble Space Telescope.
This image is the second in a yearly series of snapshots taken as part of the Outer Planets Atmospheres Legacy (OPAL) project, according to news releases from the European Space Agency and the Space Telescope Science Institute. OPAL is helping scientists to understand the atmospheric dynamics and evolution of our Solar System’s gas giant planets. In Saturn’s case, astronomers will be able to track shifting weather patterns and other changes to identify trends.
It takes a lot of detective work to figure out the nature of a type Ia supernova. Celestial Pig Pens and new tricks from old telescopes are contributing to the effort. That’s what we learned at the most recent meeting of Astronomy on Tap Seattle.
Messy Siblings: Supernovae in Binary Systems
Dr. Melissa Graham is a project science analyst for the Large Synoptic Survey Telescope, working out of the Astronomy Department at the University of Washington. Her main research focus is supernovae. In particular, she’s doing a lot of work on type Ia supernovae, which occur in binary star systems. One of the stars involved will be a carbon-oxygen white dwarf star.
“It’s a star that wasn’t massive enough to fuse anything else inside the carbon layers,” Graham explained. Outer layers of hydrogen and helium are thrown off in a planetary nebula phase, so the carbon and oxygen are what’s left.
“Carbon-oxygen white dwarf stars are very compact, very dense, about the size of the Earth but they can be up to about 1.4 times the mass of the Sun,” Graham said. These stars are pretty stable as stars go, so they don’t blow up under normal circumstances.
“When we do see these kind of supernovae that are clearly the explosion of carbon-oxygen white dwarf stars we have to wonder why,” she said. It turns out there are two possible scenarios. The binary can be a pair of carbon-oxygen white dwarf stars that spiral in on each other, merge, and then explode. Or the binary can include one white dwarf and a more typical hydrogen-rich companion star.
“In this case the companion star can feed material onto this carbon-oxygen white dwarf star, might make it go over 1.4 solar masses, become unstable, and then explode,” Graham said.
Which is which?
The key to figuring out which of these scenarios actually occurred is to take a look at the area around the supernova. If the companion is a more hydrogen-rich companion star, the neighborhood can get a little messy.
“It’s sort of like a celestial Pig Pen star that leaves a lot of material lying around,” Graham said. A blast from a supernova can interact with this material and cause it to brighten. The trouble is that astronomers typically only observe type Ia supernovae for a couple of months; they fade quickly. So if this extra material is far away from the event, they might not see the interaction. The answer is patience, to look at the supernova sites for up to 2-3 years after.
Graham did exactly that, using the Hubble Space Telescope to keep an eye on the locations of 65 type Ia supernovae.
“Out of these 65, I very luckily found one” in which there was brightening much later. They checked the spectrum of the light and found hydrogen, a sure sign that the companion in this particular type Ia supernova was a Pig Pen. Graham suspects that up to five percent of such explosions involve messy sibling stars.
“This marks a massive increase in our ability to both find and characterize supernovae,” she said.
Old scope, new tricks
While we wait for LSST an old workhorse telescope is doing interesting work in a similar vein. Professor Eric Bellm of the UW works with the Zwicky Transient Facility (ZTF), which uses the 48-inch telescope at Palomar observatory in California. The scope is a Schmidt, completed in 1948, and for years it was the largest Schmidt telescope in the world. It’s main function at first was to use its wide-field view of the sky to create maps that helped astronomers point Palomar Mountain’s 200-inch Hale Telescope.
The 48-inch was used to do numerous sky surveys over the years. It discovered many asteroids, and Mike Brown used it to find the dwarf planets he used to kill Pluto. The old photographic plates gave way to modern CCDs, and Bellm became the project scientist for the Zwicky Transient Facility—named for astronomer Fritz Zwicky, a prolific discoverer of supernovae—in 2011.
They outfitted the scope with a new camera with 16 CCDs that are four inches per side. They got some big filters for it and put in a robotic arm that could change the filters without getting in the way of the camera. They started surveying in March of last year and can photograph much of the sky on any given night.
“That’s letting us look for things that are rare, things that are changing quickly, things that are unusual,” Bellm said.
Examples of what the ZTF has found include a pair of white dwarfs that are spinning rapidly around each other, with a period of just seven minutes. They can see the orbits decay because of gravitational wave radiation. It has discovered more than 100 young type 1a supernovae. And it found an asteroid with the shortest “year” of any yet discovered; its orbit is entirely within that of Venus.
It’s doing the same sort of work that the LSST will do when it comes online.
“It’s super cool that we’ve got this more than 70 year old telescope that we’re doing cutting-edge science with thanks to the advances of technology,” Bellm said.
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington, and typically meets on the fourth Wednesday of each month at Peddler Brewing Company in Ballard. The next event is set for September 25.
As we look back at the 50th anniversary of the Apollo 11 Moon landing, Toby Smith notes that the most interesting science that came out of the mission was a bit of a surprise. Smith, a senior lecturer in astronomy at the University of Washington, gave a talk at the most recent meeting of Astronomy on Tap Seattle.
“There’s only one reason Apollo existed—to beat the Soviet Union to the surface of the Moon,” Smith noted. Few considered the mission to be scientific. “It wasn’t fully embraced by the scientific community even in its day, even among planetary scientists.”
But they figured as long as they were there, they should do some sort of science.
“This little bit of science they did fundamentally changed how we view not only the Moon, but the Earth-Moon system and our solar system,” Smith said.
The Apollo 11 landing site, the Sea of Tranquility on the Moon, is essentially an ancient lava flow, a featureless plain of cooled volcanic rock, Smith said. Think of it like Big Island of Hawaii, except you don’t really see the solidified lava on the Moon. The surface is soft, ground down and rounded off into a soft powder by billions of years of impacts. As Neil Armstrong observed just after his first step, it has the consistency of flour. That consistency almost accidentally led to the mission’s best science.
Armstrong spent about 15 minutes of the two-and-a-half hour Moon walk picking up rocks and putting them into a box. At the end he collected nine scoops of lunar regolith and dumped it into the Apollo Lunar Sample Return Container (a fancy NASA term for the case for rocks) as sort of a packing material so the larger rocks wouldn’t clatter around. If they’d taken any styrofoam peanuts he might have used those instead.
Naturally, when this material was brought back to Earth, the scientists looked at it, and Smith said it just might be the most studied geological sample ever.
Smith noted that the regolith is highly angular; lunar dust is sharp.
“This is not material that was broken up by being tumbled,” he said. “This is material that was broken up by being fractured by impacts.”
It’s a diverse sample. It contains basalt, breccia (material created by impacts that shatters and sometimes melts back together), and impact spheres. There was also one unusual, bright white material in the collection. It turned out to be anorthosite, which makes up about four percent of the sample.
“It represents a piece of the original crust of the Moon long since destroyed by four and a half billion years of impacts,” Smith explained. Anorthosite is an igneous rock, like basalt, that comes from the cooling of melted rock. Basalt is created when lava moves across the ground, but Smith noted that anorthosite doesn’t work that way.
“Anorthosite forms in big pools of lava, huge pools of lava, huge chambers of lava,” he said. “As these chambers of lava slowly cool over time, the anorthosite floats to the top.”
“If this was found on the Moon it must mean that at some point early in the Moon’s history it must have been almost completely molten,” Smith added. This information made scientists re-think their notions about the origins of the Moon.
“Before Apollo there was no indication that the whole, entire Moon was almost completely melted,” he said.
The leading theory about the formation of the Moon these days is that something pretty big, about the size of Mars, smacked into the early Earth, and that material flung into space by the impact eventually coalesced into the Moon. The catch is that computer simulations of this event don’t often result in a completely molten Moon. So more study is needed. The lunar samples have been under constant scrutiny for the last 50 years, and Smith says he’s interested to see what new information can be gleaned from those samples as new analytical technology is developed.
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington. The next gathering is set for Wednesday, August 28, 2019 at Peddler Brewing Company in Ballard.
Paris said he loves Mars and expects that humans will be going there sooner than later.
“I suspect that, the way things are going, probably in about 10 to 15 years we’re going to be on Mars,” he said, adding that he doesn’t think anyone is going to go it alone.
“Mars, in my personal opinion, is going to be an international effort, both with corporations as well as the government,” Paris said.
The book was something of a spinoff of an exhibit about Mars that Paris helped put together at the Museum of Science and Industry in Tampa. The exhibit proved pretty popular, and the book seemed the next natural step. Proceeds from book sales support the work of the Center for Planetary Science.
Paris featured fantastic 3-D images of a great many Martian geological features in his presentation. While his Ph.D. is in astronomy, he’s really morphed into something of a rock hound.
“We are primarily geologists that are studying all of the geological features here on Earth,” he said, “and we’re trying to compare and contrast them with what we see on the lunar surface, what we see on Mercury, Venus, and all of the terrestrial planets.”
Paris called the process comparative planetology.
Ripple marks such as those shown in this photo from the rover Opportunity were deposited by water moving back and forth. Image: NASA/JPL
“If I look at something here on Earth and I can determine how that thing happened,” he said, “and I see the same thing on Mars, I can deduce that the same processes have occurred, most likely.”
That caveat was included on most of his deductions, but the comparisons are pretty compelling. For example, Paris passed around a flat piece of rock with ripple marks on it that he collected in the Canyonlands in Utah. Such ripple marks are created by water moving back and forth over the rock, and the Canyonlands piece looks exactly like stuff the rovers have seen on Mars.
Paris also showed photos of rock formations made when moving or freezing water breaks up bedrock, and wears it down into small pebbles. At least, that’s how it happens on Earth.
This set of images compares the Link outcrop of rocks on Mars with similar rocks seen on Earth. Image: NASA/JPL-Caltech/MSSS and PSI
“We call that either fragmented sidewalk or conglomerate terrain,” he said. Here in Seattle, especially after our recent cold and snowy weather, we just call it a pothole, and that’s how the Emerald City is like the Red Planet! Potholes all over the place!
Paris does a lot of rock hunting in the American southwest, which has a lot of Mars analog sites that scientists and NASA use in their Mars work. These include Moenkopi in Arizona, Canyonlands, the Mojave Desert, Death Valley, and the Flagstaff area.
The website for the Center for Planetary Science notes that Paris will make a presentation in Portland in September at a time and place not yet published. Dollars to Voodoo Doughnuts it will be with Rose City Astronomers. Stay tuned.
Buying Paris’s book by clicking the link or book cover image above supports both the Center for Planetary Science and Seattle Astronomy. You can also support Seattle Astronomy’s astro-journalism with a low-cost subscription through Patreon.
Many businesses, products, and places have names rooted in space and astronomy. We’re featuring one periodically on Seattle Astronomy.
Today’s Astro Biz is Moon’s Kitchen Japanese restaurant. Moon’s Kitchen is on Fourth Avenue in Seattle’s Belltown Neighborhood.
Moon’s Kitchen has no official online presence that we could discover. That’s a little odd in this day and age; if there’s no website, does a place really exist? Probably so, as there’s a robust discussion of the joint on Yelp and the like, and it receives generally good reviews, though one grump called it a “glorified teriyaki place.” You can order Moon’s Kitchen dishes for delivery through Grub Hub, Uber Eats, and possibly others.
There’s a great new website about our solar system that will blow your socks off! The Planets Online introduces viewers to a broad range of subjects in a unique, innovative, and entertaining way. The site naturally interweaves information on science, engineering, music, visual design, and technology—it could be a showcase for STEAM education (Science, Technology, Engineering, Arts, and Math).
The site is the creation of visual artist Adrian Wyard. Followers of Seattle Astronomy may recall that we wrote about Wyard’s show The Planets Live about three years ago (story here). The concept is that Wyard uses images of celestial objects to accompany and enhance classical music. He’s done it with Gustav Holst’s The Planets, Mussorgsky’s Pictures at an Exhibition, and Dvorák’s 9th Symphony.
The core of The Planets Online is a video of a performance of The Planets by the Auburn Symphony Orchestra directed by Anthony Spain and featuring the Seattle Pacific University Women’s Choir and Wyard’s visuals. This is no ordinary video, however. If you remember when we used to get our video on plastic disks, think of The Planets Online as a video loaded with special features. As the video plays, a sidebar describes the images and who created them, offers facts about the music, pulls up Wikipedia pages and other sources about the science, throws in tidbits of trivia, and more. You can switch any of these info streams on or off depending on your interests.
Here’s a little preview video of The Planets Online.
We expect you might spend a good deal of time with the site.
There are live performances of Wyard’s work coming up this spring in Florida, Virginia, and Texas. The last northwest live performances were back in April, May, and October last year. If you missed those, you can have a little fun—and learn a few things—with The Planets Online.